9,957 research outputs found
Tunable microgel-templated porogel (MTP) bioink for 3D bioprinting applications
Micropores are essential for tissue engineering to ensure adequate mass transportation for embedded cells. Despite the considerable progress made by advanced 3D bioprinting technologies, it remains challenging to engineer micropores of 100 µm or smaller in cell-laden constructs. Here, a microgel-templated porogel (MTP) bioink platform is reported to introduce controlled microporosity in 3D bioprinted hydrogels in the presence of living cells. Templated gelatin microgels are fabricated with varied sizes (≈10, ≈45, and ≈100 µm) and mixed with photo-crosslinkable formulations to make composite MTP bioinks. The addition of microgels significantly enhances the shear-thinning and self-healing viscoelastic properties and thus the printability of bioinks with cell densities up to 1 × 108 mL−1 in matrix. Consistent printability is achieved for a series of MTP bioinks based on different component ratios and matrix materials. After photo-crosslinking the matrix phase, the templated microgels dissociated and diffused under physiological conditions, resulting in corresponding micropores in situ. When embedding osteoblast-like cells in the matrix phase, the MTP bioinks support higher metabolic activity and more uniform mineral formation than bulk gel controls. The approach provides a facile strategy to engineer precise micropores in 3D printed structures to compensate for the limited resolution of current bioprinting approaches
Penta-Hepta Defect Motion in Hexagonal Patterns
Structure and dynamics of penta-hepta defects in hexagonal patterns is
studied in the framework of coupled amplitude equations for underlying plane
waves. Analytical solution for phase field of moving PHD is found in the far
field, which generalizes the static solution due to Pismen and Nepomnyashchy
(1993). The mobility tensor of PHD is calculated using combined analytical and
numerical approach. The results for the velocity of PHD climbing in slightly
non-optimal hexagonal patterns are compared with numerical simulations of
amplitude equations. Interaction of penta-hepta defects in optimal hexagonal
patterns is also considered.Comment: 4 pages, Postscript (submitted to PRL
Vacuum Polarization and Screening of Supercritical Impurities in Graphene
Screening of charge impurities in graphene is analyzed using the exact
solution for vacuum polarization obtained from the massless Dirac-Kepler
problem. For the impurity charge below certain critical value no density
perturbation is found away from the impurity, in agreement with the linear
response theory result. For supercritical charge, however, the polarization
distribution is shown to have a power law profile, leading to screening of the
excess charge at large distances. The Dirac-Kepler scattering states give rise
to standing wave oscillations in the local density of states which appear and
become prominent in the supercritical regime.Comment: 5 pages, 2 figure
Delegating Quantum Computation in the Quantum Random Oracle Model
A delegation scheme allows a computationally weak client to use a server's
resources to help it evaluate a complex circuit without leaking any information
about the input (other than its length) to the server. In this paper, we
consider delegation schemes for quantum circuits, where we try to minimize the
quantum operations needed by the client. We construct a new scheme for
delegating a large circuit family, which we call "C+P circuits". "C+P" circuits
are the circuits composed of Toffoli gates and diagonal gates. Our scheme is
non-interactive, requires very little quantum computation from the client
(proportional to input length but independent of the circuit size), and can be
proved secure in the quantum random oracle model, without relying on additional
assumptions, such as the existence of fully homomorphic encryption. In practice
the random oracle can be replaced by an appropriate hash function or block
cipher, for example, SHA-3, AES.
This protocol allows a client to delegate the most expensive part of some
quantum algorithms, for example, Shor's algorithm. The previous protocols that
are powerful enough to delegate Shor's algorithm require either many rounds of
interactions or the existence of FHE. The protocol requires asymptotically
fewer quantum gates on the client side compared to running Shor's algorithm
locally.
To hide the inputs, our scheme uses an encoding that maps one input qubit to
multiple qubits. We then provide a novel generalization of classical garbled
circuits ("reversible garbled circuits") to allow the computation of Toffoli
circuits on this encoding. We also give a technique that can support the
computation of phase gates on this encoding.
To prove the security of this protocol, we study key dependent message(KDM)
security in the quantum random oracle model. KDM security was not previously
studied in quantum settings.Comment: 41 pages, 1 figures. Update to be consistent with the proceeding
versio
Computational Study of Tunneling Transistor Based on Graphene Nanoribbon
Tunneling field-effect transistors (FETs) have been intensely explored
recently due to its potential to address power concerns in nanoelectronics. The
recently discovered graphene nanoribbon (GNR) is ideal for tunneling FETs due
to its symmetric bandstructure, light effective mass, and monolayer-thin body.
In this work, we examine the device physics of p-i-n GNR tunneling FETs using
atomistic quantum transport simulations. The important role of the edge bond
relaxation in the device characteristics is identified. The device, however,
has ambipolar I-V characteristics, which are not preferred for digital
electronics applications. We suggest that using either an asymmetric
source-drain doping or a properly designed gate underlap can effectively
suppress the ambipolar I-V. A subthreshold slope of 14mV/dec and a
significantly improved on-off ratio can be obtained by the p-i-n GNR tunneling
FETs
Reaction-Diffusion System in a Vesicle with Semi-Permeable Membrane
We study the Schloegl model in a vesicle with semi-permeable membrane. The
diffusion constant takes a smaller value in the membrane region, which prevents
the outflow of self-catalytic product. A nonequilibrium state is stably
maintained inside of the vesicle. Nutrients are absorbed and waste materials
are exhausted through the membrane by diffusion. It is interpreted as a model
of primitive metabolism in a cell.Comment: 8 pages, 6 figure
Localized magnetic states in biased bilayer and trilayer graphene
We study the localized magnetic states of impurity in biased bilayer and
trilayer graphene. It is found that the magnetic boundary for bilayer and
trilayer graphene presents the mixing features of Dirac and conventional
fermion. For zero gate bias, as the impurity energy approaches the Dirac point,
the impurity magnetization region diminishes for bilayer and trilayer graphene.
When a gate bias is applied, the dependence of impurity magnetic states on the
impurity energy exhibits a different behavior for bilayer and trilayer graphene
due to the opening of a gap between the valence and the conduction band in the
bilayer graphene with the gate bias applied. The magnetic moment and the
corresponding magnetic transition of the impurity in bilayer graphene are also
investigated.Comment: 16 pages,6 figure
Effect of randomness and anisotropy on Turing patterns in reaction-diffusion systems
We study the effect of randomness and anisotropy on Turing patterns in
reaction-diffusion systems. For this purpose, the Gierer-Meinhardt model of
pattern formation is considered. The cases we study are: (i)randomness in the
underlying lattice structure, (ii)the case in which there is a probablity p
that at a lattice site both reaction and diffusion occur, otherwise there is
only diffusion and lastly, the effect of (iii) anisotropic and (iv) random
diffusion coefficients on the formation of Turing patterns. The general
conclusion is that the Turing mechanism of pattern formation is fairly robust
in the presence of randomness and anisotropy.Comment: 11 pages LaTeX, 14 postscript figures, accepted in Phys. Rev.
Flavor brane on the baryonic branch of moduli space
We study an extra flavor in the cascading SU((k+1)M)xSU(k M) gauge theory by
adding probe D7-brane to the geometry. By finding a solution to the
kappa-symmetry equation we establish that the D7-brane is mutually
supersymmetric with the background everywhere on the baryonic branch of moduli
space. We also discuss possible applications of this result.Comment: 15 pages; v2 typo corrected, references adde
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